Generally, packing cases are used to provide a seal along and around a movable piston rod of a gas compressor to prevent the escape of gas from the piston cylinder along and around the surface of the piston rod. Packing cases are also used to provide gas tight seals along and around the movable shafts of other rotating machinery. A packing case member or packing cup is typically cylindrically shaped and contains a central circular opening for stationary mounting in a compressor housing on a reciprocally movable piston rod. The central opening has a slightly larger diameter than that of the piston rod preventing the piston rod from rubbing against the cup as the piston rod reciprocates. The series of cups forming the packing case contains seal rings which slidably bear against the rod to provide a gas tight barrier.
The seal rings cause sliding friction to occur along the piston rod as the piston rod moves through the rings. This friction causes heating of the packing cups. To reduce heating in a lubricated compressor, liquid lubricants are typically introduced through a channel or opening in the packing case to the surface of the piston rod to reduce the sliding friction. In non-lubricated compressors, no liquid lubricant is used. Liquid coolants are introduced into passageways in the packing cups housing to absorb heat from the packing case.
One existing packing case utilizes cylindrically-shaped cups that are cast in two mating cylindrically-shaped pieces. A circular groove is machined into opposing surface portions of the mating faces of the pieces so that, when they are joined, a circular passageway is formed in the cup housing which extends around a majority peripheral portion of the central opening. One end of the passageway contains an inlet port which opens onto one flat face of the cup, while the opposite end portion of the passageway contains an outlet port which opens onto an opposite flat face of the cup. A fluid coolant introduced into the circular passageway flows between the inlet and outlet ports.
Typically, a single inlet line carrying liquid coolant is connected to each inlet port in the series of cups making up a packing case. Similarly, a single outlet line collects the coolant circulated through each cup and is connected to each of the outlet ports of each of the cups. This arrangement is called parallel flow and has the disadvantage that the passageways of one or more cups can become clogged, producing increased heating in the clogged cup or cups without it becoming immediately apparent to operators of the compressor. Because they are formed of two mated pieces, it is necessary to completely remove them from the piston rod and break them apart in order to clean the individual grooves forming the circular coolant passageways.
Another existing packing case includes a series of packing case members having separate coolant passageways that are successively linked together to form a series flow path for coolant circulating through the packing case. Each packing cup includes a housing defining a hollow passageway surrounding a majority peripheral portion of the central opening to form a path for the flow of a fluid coolant around the circular opening between a fluid inlet port and a fluid outlet port located on opposite end portions of the passageway. The inlet port and outlet port open onto an outer surface of the cup housing. The passageway is formed by a series of hollow, straight-line segments successively intersecting one another at different angular positions around the circular opening between the inlet port and the outlet port. Each of the straight-line segments includes an end portion extending to a different access opening located on at least one outer surface of the housing.
Existing packing cases assist with providing a seal for movable machinery shafts and transferring the heat generated by such shafts. As more modern machines are made with movable shafts that have faster speeds and shorter strokes and operate non-lubricated, improved heat transfer becomes increasingly important. Accordingly, there is a need for a packing case for compressors and other machinery that provides improved cooling.